1. Field of the Invention
The present invention relates to an optical switching apparatus. More particularly, the present invention relates to a 2×2 optical switching apparatus using photonic crystal structures.
2. Description of the Related Art
Optical switching apparatuses have made it possible to considerably increase information processing speed and switching capacity and to overcome limitations of conventional electric switching technology. Optical switching apparatuses have become essential for optical communication, optical exchanging, optical processing, optical processes, optical computers and so forth.
Nowadays, with Internet capacity increasing by around four to five times per year, it is anticipated that information communication having an ultra large capacity of 100 Tb/s will be required within the next 10 years. However, the ability of today's technology to support such an ultra large capacity of information communication is unfortunately limited.
Today, in the optical network field, two kinds of switches are used. One, a free-space optical switch of a MEMS (Micro Electro Mechanical System) type, has advantages of multi-channel parallel processing and multi-channel connection, but has the basic disadvantage of slow switching time, i.e., a few ms to a few μs. The other switch that is currently used is a semiconductor switch of an optical waveguide type that has advantages of high-speed processing and relatively fast switching time, i.e., a few ns to a few ps, but has the basic disadvantage of delayed processing time in geometrical progression according to an increase of a number of channels. That is, in a case of a Wavelength Division Multiplexing (WDM) network constructed with 100 channels to have a transmission capacity of 100 Tb/s as described above, about 1 THz of transmission bandwidth is needed. However, there is no technology developed for such capability yet. Therefore, it is an urgent project to secure optical switching technology capable of processing a large capacity, i.e., 100 Tb/s, of information at a very high-speed, such as 1 THz, within the next few years.
In an optical network, application fields of optical switching include a protection switch, an optical add/drop multiplex (OADM), an optical crossconnect, etc., and particularly, a 2×2 optical switch may be used in access for line recovery and also as an OADM in a metro network.
The 2×2 optical switch, which has a structure connecting two input ports and two output ports, changes the connection state of the input ports and the output ports according to switching states. The representative technologies applied in the 2×2 optical switch at present are largely classified into bulk-mechanical/opto-mechanical technology, two dimensional micro electro mechanical systems (2D-MEMS) technology, thermo-optic waveguide technology and bubble technology.
The bulk-mechanical/opto-mechanical technology uses a method of changing optical route by using a motor, an electromagnetic-force driven device, or a piezo to directly drive an optical fiber, a mirror, or a lens. Therefore, the bulk-mechanical/opto-mechanical technology has disadvantages in that mechanical motions easily result in performance degradation of the moving sections, and elements used therein are expensive. The 2D-MEMS also has a problem in reliability guarantee because it too has a moving section. Meanwhile, the thermo-optic waveguide technology is profitable in mass production, but is affected by changes of ambient temperature and consumes relatively large power so as to generate heat. The bubble technology has bad optical properties, such as insertion loss, crosstalk and so forth.